1. Field of the Invention
The present invention relates to a method and an apparatus for manufacturing a device having a moveable structure, and in particular a micro-mechanical device.
2. Description of the Related Art
Numerous devices, in particular micromechanical devices, comprise movable structures or structures sensible for mechanical load or deformation. Among those are micro-mechanical actuators and sensors having membranes, freely vibrating springs, structures suspended on springs etc. One example for a micro-mechanical sensor is an Si microphone. These devices are generally at first manufactured with a protective structure, for example a sacrificial layer or a varnish plug, which carries the movable structure during the manufacturing process or supports the same, respectively, and thus prevents a mechanical deformation or damage of the movable structure.
During the manufacturing of a micro-mechanical device large mechanical forces may act on the same and on the moveable structure, which may for example be caused by a holding tool, a static or dynamic fluid pressure or a surface tension at a phase interface between a liquid and a gaseous medium. In the intermediate device, i.e. the uncompleted device, the protective structure absorbs these forces and thus prevents an excessive load or deformation, respectively, of the moveable structure which may otherwise lead to a tearing or breaking of the moveable structure. After a completed structuring of the intermediate device using the protective structure, the same is removed or resolved from the same, respectively, in order to release the removable structure and thus obtain the completed device. The resolving of the protective structure is usually performed in a wet-chemical process. After releasing the protective structure the moveable parts of the device are very sensitive, for example, against fluid streams or against a short-term drying when converting from a liquid medium into another.
Finally, the device has to be dried, wherein the problem occurs that with a simple drying process, at the interface between a liquid medium and a gaseous medium a surface tensions occurs which may exert great forces on the moveable structure and for example cause an adhesion of the micro-mechanical or moveable structure, respectively, to fixed areas of the device. The occurrence of an interface between a liquid and a gaseous phase may for example be prevented using the “Super Critical Point Drying”, wherein by applying a pressure which is higher than the critical pressure of the substance to be removed and a temperature which is higher than the critical temperature of the substance to be removed, the substance to be removed is transferred from the liquid into the gaseous state by preventing a phase boundary from liquid to gaseous. Finally, the devices are diced and set up within casings.
The handling of the devices with the freed micro-mechanical or moveable structures, respectively, in the above-described method is problematic, as the moveable structure must not become wet anymore and must not be exposed to greater mechanical loads in any other way. Exactly this is, however, what generally happens when dicing the devices from a substrate or wafer, respectively, by sawing. From this, a great risk of damaging devices results. This problem is new, for example for Si microphones, and has not been solved up to now.
US 2001/0029060 A1 describes a manufacturing method for an acceleration sensor. The acceleration sensors processed on a substrate are here separated from each other in an intermediate state. In this intermediate state moveable parts of the acceleration sensor are protected from damage by a protective layer. After the separation process, the sensors are arranged in an chip tray. The further etching processes required for completing the sensors are performed while the sensors are present within the chip tray.
JP 7176511 A describes a chip tray in the form of a two-piece device holding means having approximately conical through-holes in which devices may be held which are simultaneously blown at by air nozzles and thereby dried.